Analysis of curium in mixed oxide fuel irradiated in the experimental fast reactor JOYO for the evaluation of its transmutation behavior

Curium isotopes generated in the MOX fuel irradiated in the experimental fast reactor JOYO were analyzed by applying a sophisticated radiochemical technique. Curium was isolated from the irradiated MOX fuel by anion-exchange chromatography using a mixed medium of nitric acid and methanol. The isotopic ratio of curium and its content were determined by thermal ionization mass spectroscopy and alpha-spectrometry, respectively. The curium content was less than 0.004 at% even at high burnup of 120 GWd/t, which is much smaller than that of PWR-MOX at 60 GWd/t. On the basis of present analytical results, the transmutation behavior of curium isotopes in a fast reactor was discussed from various viewpoints. Transmutation rates of curium isotopes were estimated; the rate for (246)cm, which is known to be a key nuclide in the transmutation of curium, was larger than the previously reported value. It was concluded from these evaluations that the fast reactor was suitable for the incineration of curium.